1. Field of the Invention
The present invention relates to the field of door locks and, more particularly, to handle door lock types.
2. Prior Art
In the past, external door locks utilizing a thumb piece actuator and key mechanism were normally locked by blocking operation of the external thumb piece actuator. When one attempted to force open a door with a lock which was in the locked position, all that was needed to damage the lock was to press down the thumb piece actuator with more force than the blocking mechanism was constructed to withstand. This would cause the lock mechanism, which is generally activated by the thumb piece actuator, to bend or break, thereby permitting illegal entry, or to become inoperative resulting in the necessity of complete removal of the lock mechanism and replacement of the bent or broken parts. In addition, especially during the construction phase of buildings having multiple lock installations, the thumb piece actuator has become a prime subject of vandalism. For example, a vandal would attempt to enter into the locked area by striking the thumb piece actuator. In most instances, the thumb piece actuator will merely bend or break and entry will not be achieved. However, the thumb piece actuator, as well as other parts, may have to be completely replaced. Consequently, it has long been the practice in the prior art to use expensive and bulky thumb piece actuators and blocking mechanisms in an attempt to eliminate, or at least substantially reduce the vandalism encountered in forceable entry attempts. Of course, this is expensive and does not completely prevent vandalism and illegal entry inasmuch as a vandal is likely to strike the thumb piece actuator with a heavy blunt instrument. If such was the case, the lock mechanism itself may be severly damaged requiring the complete door lock to be removed and repaired or replaced. The necessity of complete removal accentuates the problems associated with the prior art thumb piece actuators which are immovable when the lock mechanism is in the locked position.
Another aspect of prior art external door locks is that they require at least two holes to be drilled in the door so as to communicate with the outside escutcheon; one hole for the door knob and a second hole for the lock cylinder assembly. The second hole is necessary inasmuch as the prior art lock cylinder assemblies are too large to fit into the outside excutcheon. The prior art lock cylinder assemblies consist of a complicated series of metal bars and levers which are activated and set into motion when the lock cylinder is rotated. These bars and levers are expensive, subject to malfunction, and take up much of the space in the escutcheon housing. Because of the exactness required for placement of the holes in the door, expensive equipment is also required to drill the required holes for the lock assemblies. In addition, there is considerable time required for determining the exact location of the holes, and therefore, any extra holes can add significantly to the cost and complexity of installation. This problem is especially acute when one considers that an improperly drilled hole can cause the entire lock mechanism to be rendered inoperative. Further, expensive repairs may be required to patch an undesired hole in the door before a second attempt of installation can be made. It is thus apparent that any prior art door lock which requires extra holes to be drilled in the door for the lock cylinder mechanism suffers severe shortcomings.
The present invention encompasses novel improvements for a door lock which offers desirable characteristics heretofore lacking in the prior art locks.